Repression of c-myc is necessary but not sufficient for terminal differentiation of B lymphocytes in vitro

The importance of c-myc as a target of the Blimp-1 repressor has been studi ed in BCL-1 cells, in which Blimp-1 is sufficient to trigger terminal B-fel l differentiation. Our data show that Blimp-1-dependent repression of c-myc is required for BCL-1 differentiation, since constitutive expression of c- Myc blocked differentiation. Furthermore, ectopic expression of cyclin E mi micked the effects of c-Myc on both proliferation and differentiation, indi cating that the ability of c-Myc to drive proliferation is responsible for blocking BCL-1 differentiation. However, inhibition of c-Myc by a dominant negative form was not sufficient to drive BCL-1 differentiation. Thus, duri ng Blimp-1-dependent plasma cell differentiation, repression of c-myc is ne cessary but not sufficient, demonstrating the existence of additional Blimp -1 target genes.